Simplify the following expression: $k = \dfrac{ac + 2bc}{2ac + 2c^2} - \dfrac{4bc + c^2}{2ac + 2c^2}$ You can assume $a,b,c \neq 0$.
Since the expressions have the same denominator we simply combine the numerators: $k = \dfrac{ac + 2bc - (4bc + c^2)}{2ac + 2c^2}$ $k = \dfrac{ac - 2bc - c^2}{2ac + 2c^2}$ The numerator and denominator have a common factor of $c$, so we can simplify $k = \dfrac{a - 2b - c}{2a + 2c}$